It was one of the summer's top stories. In August, two British academics announced that men are significantly cleverer than women and that male university students outstrip females by almost five IQ points. 'Girls need manpower' and 'IQ tests: women just don't get it' claimed the headlines.

The announcement was the latest round in a battle that has come to dominate psychology in recent years and has triggered countless workplace arguments and marital rows over the years. In this case, the formidable nature of the statistics used by the study's authors - Dr Paul Irwing and Professor Richard Lynn - seemed to land a fairly hefty blow for the men-are-cleverer camp.

'It confirms what we've long suspected,' said a (male) writer in the Sun. 'The male of the species is cleverer than the female. It's a no-brainer.'

But not any more. Last week the work of the two academics was denounced in startlingly fierce terms in the journal Nature just as a paper officially outlining their work was published in the British Journal of Psychology

The attack - which claims that Irwing and Lynn's work is 'deeply flawed' - is unusual. Science journals rarely attack studies at the same time as they are being published by a rival. Neither do they often use strong or intemperate terms. A delayed and measured approach is the norm in scientific circles.

Nevertheless, Nature insisted that its confrontational approach was justified. Supposed sex differences in IQ attract wide attention and are likely to be widely cited, it pointed out. 'We were made aware that Irwing and Lynn's results were based on a seriously flawed methodology, and had the opportunity to provide timely expert opinion when their paper became publicly available,' said Tim Lincoln of Nature's News & Views section.

The author of the Nature article was even more critical. 'Their study - which claims to show major sex differences in IQ - is simple, utter hogwash,' said Dr Steve Blinkhorn, an expert on intelligence testing. The study by Irwing, of Manchester University, and Lynn, an Ulster academic who has previously claimed that white people are cleverer than black people, was based on a technique known as meta-analysis. The pair examined dozens of previous studies of men's and women's IQs, research that had been carried out in different countries - including Egypt, Belgium, Australia and the United States - between 1964 and 2004 and published in a variety of different journals. Then they subjected these studies to an intense statistical analysis.

From this, the pair decided that their work showed men outnumber women in increasing numbers as intelligence levels rise. According to Irwing and Lynn, there are twice as many men with IQ scores of 125 - a level typical for people with first-class degrees - than women, while at the level of 155, an IQ associated with genius, there were 5.5 men for every woman.

The announcement was startling because it had been previously accepted that there were few differences between male and female IQs. Most research on the subject of the intellectual differences between the sexes had concentrated on other aspects of brain activity.

Professor Simon Baron-Cohen, a psychologist at Cambridge University, has recently argued that levels of testosterone in the womb will determine how much eye contact a child will make or how quickly his or her language will develop. Hence more newborn boys look longer at objects, and more newborn girls look at faces.

By contrast, Professor Steve Jones, a geneticist at University College London, and the author of Y: The Descent of Men, says there is absolutely no consensus at all about the science. 'That doesn't mean there are no differences between the brains of the sexes, but we should take care not to exaggerate them.'

However, it was not just the nature of their findings that was unexpected; the two psychologists' approach to publishing their work was unusual. They did not release their paper to fellow academics immediately. Instead, they gave it out to journalists two months before it was scheduled to be published in the British Journal of Psychology this month.

'In retrospect, that may have seemed a peculiar thing to do,' Irwing told The Observer. Last week was therefore fellow academics' first chance to to make an assessment of their work and respond.

After reports of their study were published in newspapers, Irwing and Lynn appeared on various radio and TV shows. In general, they received responses that were fairly uncritical and were only occasionally pushed to defend their claims. At one point, Lynn alleged that men were smarter simply because they have bigger brains and said that girls now outperform boys at school because of the inclusion of coursework, to which more conscientious females were better suited.

However, last week's publication of Blinkhorn's critique in Nature represents a major change in attitudes to their claims. He points to a number of 'serious flaws' in the approach taken by Lynn and Irwing. For a start, he accuses them of carefully selecting those IQ studies that they allowed in their meta-analysis.

In particular, he says they chose to ignore a massive study, carried out in Mexico, which showed there was very little difference in the IQs of men and women. 'They say it is "an outlier" in data terms --in other words, it was a statistical freak,' Blinkhorn said.

'It was nothing of the kind. It was just plain inconvenient. Had it been included, as it should have been, it would have removed a huge chunk of the differences they claim to have observed.'

In addition, Blinkhorn said the pair were ignoring a vast body of work that had found no differences. 'Psychologists often carry out studies that find no differences between men's and women's IQs but don't publish them for the simple reason that finding nothing seems uninteresting. But you have to take these studies into account as well as those studies that do find differences. But Lynn and Irwing did not. That also skewed their results.'

Blinkhorn also accuses the pair of adopting a variety of statistical manoeuvres that he describes, in his paper, as being 'flawed and suspect'.

Last week Irwing defended the study and accused Blinkhorn of 'attacking the men, not the science'. The study they had done 'also has to be seen in context of our other work which has shown significant sex differences in IQ. Nor is it true that we played about with our data.'

For his part, Blinkhorn is unrepentant. 'Sex differences in average IQ, if they exist at all, are too small to be interesting,' he states in Nature

It is a stark, unequivocal statement - although it will certainly not be the last word in a debate that seems likely to dog psychology for years to come.

Scuffles in science

The Nature attack is the latest of several recent rows that have erupted over papers in leading journals. In 1998, Andrew Wakefield caused a furore when he wrote an article in the Lancet claiming a link between autism and the MMR vaccine. The paper led to a boycott of the vaccine by many parents, although scientists have been unable to establish any of his claims. Critics attacked the Lancet for publishing the paper.

The journal was also criticised by Nobel laureate Aaron Klug for printing a paper claiming the immune systems of rats were damaged after they were fed genetically modified potatoes. The claims have never been substantiated.

In contrast, last year's Nature paper, in which scientists revealed they had found remains of a race of tiny apemen, Homo floresiensis, pictured left, has survived scrutiny despite claims that the fossils really belonged to deformed Homo sapiens. Research has since confirmed the original paper's results.